持久性有机污染物机械化学分解过程中自由基的产生和作用机理研究

Mechanochemical destruction(MCD) technology has the advantages of low temperature, non-combustion characteristic, decomposing the persistent organic pollutants (POPs) and avoiding the generation and emission of dioxins by-products, which provides a new way for the environmental sound disposal of POPs waste in China. However, it is the key to control the mechanochemical reaction conditions to generate and transfer active free radicals, promote dehalogenation and enhance destruction of POPs. The project focuses on the free radical reaction mechanism in the process of hexachlorobenzene mechanochemical destruction. It will study the interaction mechanism between hexachlorobenzene and typical oxides additives, analyze the characteristics of free radical generation and transmission under the external mechanical forces and explore the impacts of free radicals on the hexachlorobenzene’s dechlorination & hydrogenation, halogen inorganic transformation, carbon chlorine condensation and carbonization of final products. The project will make the molecular dynamics model of the free radical-based dechlorination process, propose the POPs mechanochemical destruction reaction macroscopic rate equation and explore the synergistic reaction conditions to improve both of destruction rate of POPs and minimization of harmful residues, which will lay a theoretical basis for further in-depth study and practical application of POPs waste mechanochemical destruction technology.

机械化学分解反应具有低温、非焚烧的特征，在分解破坏持久性有机污染物(POPs)的同时避免了二噁英类副产物的产生和排放，为我国POPs废物的无害化处置提供了一条新的途径。但机械化学反应过程中如何高效产生自由基和促进POPs的活化脱卤，本征机理尚不明确。本项目以六氯苯机械化学分解反应过程中的自由基演变规律为核心，研究六氯苯与典型金属和氧化物添加剂体系的相互作用关系，分析机械外力下自由基的产生和传递特性，探索自由基反应对于POPs脱氯加氢、卤素无机化和产物碳化等过程的影响和作用机制，构建POPs机械化学分解反应分子动力学和宏观速率模型，探索同时提高POPs分解速率和降低有害污染物残留的协同反应途径，为POPs废物机械化学分解新方法的进一步深入研究奠定理论基础。

机械化学分解反应具有低温、非焚烧的特征，在分解破坏持久性有机污染物(POPs)的同时避免了二噁英类副产物的产生和排放，为我国POPs废物的无害化处置提供了一条新的途径。本项目研究了六氯苯机械化学分解反应过程中的自由基演变规律，分析了机械力作用下系统中自由基的产生和传递特性，探索了自由基反应对于POPs脱氯加氢、卤素无机化和产物碳化等过程的影响和作用机制。研究表明，机械化学反应过程中POPs与反应助剂发生表面电荷转移，生成大量高活性苯氧自由基。实验室仪器分析和量子化学理论计算表明，六氯苯的机械化学法脱氯主要遵循氯代苯氧自由基的脱氯机制，反应产物主要为邻位低氯苯。苯氧自由基的生成涉及到了碳氯键的断裂和碳氧键的生成，反应过程中有两个能垒，活化能分别为39.4和3.4 kJ/mol。本项目还探索了同时提高六氯苯分解速率和降低有害污染物残留的协同反应途径，构建了POPs机械化学分解反应分子动力学和宏观速率模型，提出了机械化学法高效修复高浓度六氯苯污染土壤的技术路线。项目研究成果可以为POPs废物机械化学分解新方法的机理研究和技术应用提供一定的理论基础和技术支撑。